Resistance based process control device diagnostics
First Claim
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1. A process control device in a process control system, comprising:
- an electrical element having an electrical resistance;
a device output adapted to couple the device to a process control loop;
an ambient temperature sensor configured to sense an ambient temperature which affects the electrical resistance of the electrical element;
an electrical element self-heater coupled to the electrical element configured to provide a self-heating signal related to a self-heating index of the electrical element due to the electrical resistance and as a function of the sensed ambient temperature, the sensed ambient temperature correcting for errors in the measurement of the self-heating index;
element diagnostics coupled to the self-heater responsively providing a diagnostic output related to health of the electrical element as a function of the self-heating signal.
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Abstract
A device in a process control system includes an electrical element which has a resistance. Self-heating circuitry coupled to the element provides a self-heating current to determine the self-heating index (SHI) of the element. Diagnostic information about the electrical element is provided based upon the self-heating index.
260 Citations
37 Claims
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1. A process control device in a process control system, comprising:
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an electrical element having an electrical resistance;
a device output adapted to couple the device to a process control loop;
an ambient temperature sensor configured to sense an ambient temperature which affects the electrical resistance of the electrical element;
an electrical element self-heater coupled to the electrical element configured to provide a self-heating signal related to a self-heating index of the electrical element due to the electrical resistance and as a function of the sensed ambient temperature, the sensed ambient temperature correcting for errors in the measurement of the self-heating index;
element diagnostics coupled to the self-heater responsively providing a diagnostic output related to health of the electrical element as a function of the self-heating signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for diagnosing an electrical element in a process control device, comprising:
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sensing an ambient temperature which affects a resistance of the electrical element;
obtaining a self-heating index (SHI) for an electrical element of the device, the sensed ambient temperature correcting for errors in the measurement of the self-heating index;
providing an electrical element diagnostic output as a function of the SHI. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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26. A device for use in a process control system, comprising:
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a loop I/O configured to coupled to a process control loop;
an electrical element having a resistance;
a current source coupled to the electrical element to inject a current into the electrical element;
a voltage sensor coupled to the electrical element having an output related to voltage drop across the electrical element;
an ambient temperature sensor configured to sense a temperature which affects the resistance of the electrical element; and
element diagnostics having a self-heating (SH) index output as a function of injected current and the voltage drop across the electrical element due to the resistance, the SH output corrected for errors as a function of the sensed ambient temperature. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification